Nested structs in query params fail to encode

[WarningImHack3r]

Such a YAML endpoint fails to encode on client request invocation, leading to a error formatting 'param_id': unsupported type Header error with a nested struct:

...
paths:
 /my/endpoint:
 post:
 security: []
 operationId: myOpId
 parameters:
 - name: param_id
 in: query
 style: form
 schema:
 $ref: "#/components/schemas/ParentStruct"
...

with ParentStruct being generated like:

type ParentStruct struct {
 Header Header `json:"header"` // a simple struct with a few fields
}

(I don't own and can't modify the YAML, I know such a use case is very unconventional)

Call stack:

// my code
client.MyEndpointWithResponse
 // generated code
 c.MyEndpoint(ctx, params, reqEditors...)
 NewMyEndpointRequest(c.Server, params)
 // starting from here we're inside `styleparam.go` from this repo
 runtime.StyleParamWithLocation("form", true, "param_id", runtime.ParamLocationQuery, *params.ParamId)
 styleStruct(style, explode, paramName, paramLocation, value)
 primitiveToString(value) // <-- value is my Header here
 // inside this function, it correctly passes into the `case reflect.Struct`, but fails because it doesn't conform to `uuid.UUID` nor to `json.Marshaler` (for some reason)
 // as a result, it `fallthrough`s in `default:` and also fails the conformity check to `fmt.Stringer`, leading to the error.

I didn't inspect the code that much, but I fail to understand why the serialization process uses the custom reflection logic instead of simply using json.Encode which would 100% do the job.

Thank you in advance!

[mromaszewicz]

That spec isn't valid OpenAPI. I realize you don't control it, but I really don't know what to do for undefined behavior. OpenAPI says that form parameters are simple types or flat objects, not nested objects, so we don't have code to detect this case.

If I assume some behavior, it will likely be wrong for some server, or some client, because being undefined, anyone can do what they want.

In this particular case, you could either edit the spec to use a Content-Type based parameter (like application/json) and marshal it as JSON, or you add a helper file alongside the generated code where you define fmt.Stringer for the generated model for param_id which converts it to a string.

I really can't fix this generically, so what I'll be doing is throwing a more meaningful error.

[WarningImHack3r]

Oh, I didn't know that: thanks for the info and the explicit error!